| 1. ninth planet in the solar system; (Greek Mythology) god of wealth and god of the underworld who is also identified with Hades. plutoyou can click anywhere, but just don't click here.pluto pluto , n. [l., fr. gr. .] (class. myth.) the son of saturn and rhea, brother of jupiter and neptune; the dark and gloomy god of the lower world.pluto monkey (zo?l.), a long-tailed african monkey (cercopithecus pluto), having side whiskers. the general color is black, more or less grizzled; the frontal band is white |